1 # SPDX-License-Identifier: GPL-2.0 2 # ========================================================================== 3 # make W=... settings 4 # 5 # There are four warning groups enabled by W=1, W=2, W=3, and W=e 6 # They are independent, and can be combined like W=12 or W=123e. 7 # ========================================================================== 8 9 # Default set of warnings, always enabled 10 KBUILD_CFLAGS += -Wall 11 KBUILD_CFLAGS += -Wundef 12 KBUILD_CFLAGS += -Werror=implicit-function-declaration 13 KBUILD_CFLAGS += -Werror=implicit-int 14 KBUILD_CFLAGS += -Werror=return-type 15 KBUILD_CFLAGS += -Werror=strict-prototypes 16 KBUILD_CFLAGS += -Wno-format-security 17 KBUILD_CFLAGS += -Wno-trigraphs 18 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,) 19 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) 20 KBUILD_CFLAGS += -Wmissing-declarations 21 KBUILD_CFLAGS += -Wmissing-prototypes 22 23 ifneq ($(CONFIG_FRAME_WARN),0) 24 KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN) 25 endif 26 27 KBUILD_CPPFLAGS-$(CONFIG_WERROR) += -Werror 28 KBUILD_CPPFLAGS += $(KBUILD_CPPFLAGS-y) 29 KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds 30 31 ifdef CONFIG_CC_IS_CLANG 32 # The kernel builds with '-std=gnu11' so use of GNU extensions is acceptable. 33 KBUILD_CFLAGS += -Wno-gnu 34 else 35 36 # gcc inanely warns about local variables called 'main' 37 KBUILD_CFLAGS += -Wno-main 38 endif 39 40 # These result in bogus false positives 41 KBUILD_CFLAGS += $(call cc-disable-warning, dangling-pointer) 42 43 # Variable Length Arrays (VLAs) should not be used anywhere in the kernel 44 KBUILD_CFLAGS += -Wvla 45 46 # disable pointer signed / unsigned warnings in gcc 4.0 47 KBUILD_CFLAGS += -Wno-pointer-sign 48 49 # In order to make sure new function cast mismatches are not introduced 50 # in the kernel (to avoid tripping CFI checking), the kernel should be 51 # globally built with -Wcast-function-type. 52 KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type) 53 54 # The allocators already balk at large sizes, so silence the compiler 55 # warnings for bounds checks involving those possible values. While 56 # -Wno-alloc-size-larger-than would normally be used here, earlier versions 57 # of gcc (<9.1) weirdly don't handle the option correctly when _other_ 58 # warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX 59 # doesn't work (as it is documented to), silently resolving to "0" prior to 60 # version 9.1 (and producing an error more recently). Numeric values larger 61 # than PTRDIFF_MAX also don't work prior to version 9.1, which are silently 62 # ignored, continuing to default to PTRDIFF_MAX. So, left with no other 63 # choice, we must perform a versioned check to disable this warning. 64 # https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au 65 KBUILD_CFLAGS-$(call gcc-min-version, 90100) += -Wno-alloc-size-larger-than 66 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH) 67 68 # Prohibit date/time macros, which would make the build non-deterministic 69 KBUILD_CFLAGS += -Werror=date-time 70 71 # enforce correct pointer usage 72 KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) 73 74 # Require designated initializers for all marked structures 75 KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) 76 77 # Warn if there is an enum types mismatch 78 KBUILD_CFLAGS += $(call cc-option,-Wenum-conversion) 79 80 KBUILD_CFLAGS += -Wextra 81 KBUILD_CFLAGS += -Wunused 82 83 # 84 # W=1 - warnings which may be relevant and do not occur too often 85 # 86 ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),) 87 88 KBUILD_CFLAGS += -Wmissing-format-attribute 89 KBUILD_CFLAGS += -Wmissing-include-dirs 90 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable) 91 92 KBUILD_CPPFLAGS += -Wundef 93 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 94 95 else 96 97 # Some diagnostics enabled by default are noisy. 98 # Suppress them by using -Wno... except for W=1. 99 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable) 100 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable) 101 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned) 102 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow) 103 ifdef CONFIG_CC_IS_GCC 104 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation) 105 else 106 # Clang checks for overflow/truncation with '%p', while GCC does not: 107 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111219 108 KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow-non-kprintf) 109 KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation-non-kprintf) 110 endif 111 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation) 112 113 KBUILD_CFLAGS += -Wno-override-init # alias for -Wno-initializer-overrides in clang 114 115 ifdef CONFIG_CC_IS_CLANG 116 # Clang before clang-16 would warn on default argument promotions. 117 ifneq ($(call clang-min-version, 160000),y) 118 # Disable -Wformat 119 KBUILD_CFLAGS += -Wno-format 120 # Then re-enable flags that were part of the -Wformat group that aren't 121 # problematic. 122 KBUILD_CFLAGS += -Wformat-extra-args -Wformat-invalid-specifier 123 KBUILD_CFLAGS += -Wformat-zero-length -Wnonnull 124 # Requires clang-12+. 125 ifeq ($(call clang-min-version, 120000),y) 126 KBUILD_CFLAGS += -Wformat-insufficient-args 127 endif 128 endif 129 KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) 130 KBUILD_CFLAGS += -Wno-tautological-constant-out-of-range-compare 131 KBUILD_CFLAGS += $(call cc-disable-warning, unaligned-access) 132 KBUILD_CFLAGS += -Wno-enum-compare-conditional 133 KBUILD_CFLAGS += -Wno-enum-enum-conversion 134 endif 135 136 endif 137 138 # 139 # W=2 - warnings which occur quite often but may still be relevant 140 # 141 ifneq ($(findstring 2, $(KBUILD_EXTRA_WARN)),) 142 143 KBUILD_CFLAGS += -Wdisabled-optimization 144 KBUILD_CFLAGS += -Wshadow 145 KBUILD_CFLAGS += $(call cc-option, -Wlogical-op) 146 KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) 147 148 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 149 150 else 151 152 # The following turn off the warnings enabled by -Wextra 153 KBUILD_CFLAGS += -Wno-missing-field-initializers 154 KBUILD_CFLAGS += -Wno-type-limits 155 KBUILD_CFLAGS += -Wno-shift-negative-value 156 157 ifdef CONFIG_CC_IS_GCC 158 KBUILD_CFLAGS += -Wno-maybe-uninitialized 159 endif 160 161 endif 162 163 # 164 # W=3 - more obscure warnings, can most likely be ignored 165 # 166 ifneq ($(findstring 3, $(KBUILD_EXTRA_WARN)),) 167 168 KBUILD_CFLAGS += -Wbad-function-cast 169 KBUILD_CFLAGS += -Wcast-align 170 KBUILD_CFLAGS += -Wcast-qual 171 KBUILD_CFLAGS += -Wconversion 172 KBUILD_CFLAGS += -Wpacked 173 KBUILD_CFLAGS += -Wpadded 174 KBUILD_CFLAGS += -Wpointer-arith 175 KBUILD_CFLAGS += -Wredundant-decls 176 KBUILD_CFLAGS += -Wsign-compare 177 KBUILD_CFLAGS += -Wswitch-default 178 179 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 180 181 else 182 183 # The following turn off the warnings enabled by -Wextra 184 KBUILD_CFLAGS += -Wno-sign-compare 185 KBUILD_CFLAGS += -Wno-unused-parameter 186 187 endif 188 189 # 190 # W=e - error out on warnings 191 # 192 ifneq ($(findstring e, $(KBUILD_EXTRA_WARN)),) 193 194 KBUILD_CFLAGS += -Werror 195 196 endif
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